This invention relates in general to a pressure relief valve for airtight containers, and deals more particularly with a pressure relief valve for airtight containers which allows for the selective equalization of interior and exterior container pressures when operated.
Pressure relief valves are utilized in many differing applications to maintain a uniform pressure regimen between an interior and an exterior of airtight containers, compartments or other enclosures. The failure of these pressure relief valves, or their absence altogether from a container, may cause significant damage to the structural integrity of containers which experience even a subtle or a momentary change in either the interior or exterior pressures exerted thereon. Of course, damage to the assets within the container may be inflicted by changes in the pressure differential alone, or rather, may be indirectly inflicted owing to the deformation of the container structure during such pressure changes. It is therefore of supreme importance that effective and reliable pressure management be employed by any airtight container which may experience pressure fluctuations.
There are several factors which may contribute to an airtight container experiencing a change in pressure between its interior and its exterior, such as a change in the ambient pressure or a change in the ambient temperature. Changes in the ambient pressure may be attributed to either a barometric change in the vicinity of the container, or to the container itself being moved to a different altitude, typically during airline flights or as a result of the container being submerged under water. When the container is subjected to extended periods of temperatures lower than that which accompanied the closing of the container, a negative pressure regimen may be produced in the container""s interior and make opening the container difficult.
Known pressure relief assemblies commonly utilize a manual or automatic valve to compensate for changes in pressure. Two-way automatic valves are designed to open when the pressure differential between the interior and exterior of the container exceeds a predetermined amount, thereby protecting the container vessel from pressure-induced damage which is outside this predetermined range. Such two-way valves are especially useful for very large containers that are transported in un-pressurized aircraft. These valves are termed xe2x80x98two-wayxe2x80x99, as they must permit the flow of air out of the container upon ascent of the aircraft while allowing airflow into the container during descent. Many two-way valves include a manually operable button or the like which pushes open the sealing member of the valve to completely equalize the air pressure in the interior and the exterior of the container.
While sufficient for many uses, known two-way valves suffer when subjected to water submersion. A container with an automatic two-way valve having a cracking pressure of approximately 0.5 psi will allow seepage into the container if submerged more than 14 inches under water, a potentially disastrous situation.
Manual pressure relief valves are typically maintained in a closed position, and then opened before the container is transported by aircraft. If the manual valve is left closed during flight, a container may be subjected to several psi of internal pressure which may cause the container""s cover to open at least enough for some air to leak out past the container""s gasket and thereby provide some measure of pressure equalization. During descent, however, the cover will be pressed tightly upon the gasket and the container will have a great negative internal pressure, possibly causing damage to the container itself or to the assets held therein. Thus, manual pressure relief valves suffer from the potential problem that the valve will not be actuated at the appropriate times prior to and following air transport.
It will therefore be readily apparent that both automatic two-way valves, as well as manual pressure relief valves, cannot protect containers in all situations.
While large cargo containers transported by aircraft typically are provided with automatic two-way valves, manual valves are commonly utilized in small, hand carried containers for a variety of reasons. Some of these containers may be utilized in aquatic sports and thus may be submerged at some time during their lifetime. As a whole, many of the hand carried containers are stored in the passenger areas of an aircraft and so do not experience the pressure differential which is commonly required to trigger the automatic two-way valves. In addition, manual relief valves are oftentimes much more inexpensive than their automatic counterparts and perform admirably provided they are opened and closed at the appropriate times.
FIG. 1 illustrates one such known manual valve assembly 10, including a knob portion 12, a gasket 14 and a threaded screw 16. As depicted in FIG. 1, when the knob portion 12 is screwed down tightly against a wall of a container, the gasket 14 prevents the passage of any air, in either direction, past the threads of the screw 16. When the knob portion 12 is somewhat loosened air is allowed to pass along the threads of the screw 16, the passage rate being increased by an optional axial slot 18 formed in the screw 16.
The manual valve assembly 10 is prone to inoperative damage as the typically metal threads of the screw 16 may strip the joint between the threads and the container wall should the valve assembly 10 be over-tightened, thus inhibiting a tight seal between the gasket 14 and the container wall and allowing for the unintended passage of air. Also of concern with the known manual valve assembly 10 of FIG. 1 is that the valve assembly 10 is not captivated to the container wall and may therefore become completely unscrewed through excessive manual operation, vibration or the like, and subsequently lost.
With the forgoing problems and concerns in mind, it is the general object of the present invention to provide a pressure relief valve which overcomes the above-described concerns and drawbacks, without compromising economic viability and operational effectiveness.
It is an object of the present invention to provide a pressure relief valve for airtight containers.
It is another object of the present invention to provide a pressure relief valve for airtight containers which is manually operable.
It is another object of the present invention to provide a pressure relief valve for airtight containers which may not be dislodged from its anchoring position.
It is another object of the present invention to provide a pressure relief valve for airtight containers which contains a minimum number of constituent parts and is therefore economic to manufacture.
It is another object of the present invention to provide a pressure relief valve for airtight containers which does not require excessive force to operate.
It is another object of the present invention to provide a pressure relief valve for airtight containers which may be tightly affixed, yet will not damage the container at its anchoring position.
It is another object of the present invention to provide a pressure relief valve for airtight containers which will not strip away from the container at its anchoring position.
According to one embodiment of the present invention a pressure relief valve includes a center hub portion which extends through an aperture formed in a wall of a container. The pressure relief valve further includes a knob having an underside from which the center hub portion extends, a static cavity formed in the underside and a pressure release cavity also formed the underside. A sealing member is fixed to the underside, and encompasses the center hub portion and the static cavity.
These and other objectives of the present invention, and their preferred embodiments, shall become clear by consideration of the specification, claims and drawings taken as a whole.